1. Field of the Invention
The present invention relates to an apparatus and method for forming a coating film such as a photoresist film and interlayer dielectric on a substrate such as a semiconductor wafer.
2. Description of the Related Art
In the manufacturing process of a semiconductor device, a dielectric film such as an interlayer dielectric film is spin-coated on a semiconductor wafer by, for example, the sol-gel method, the silk method, the speed film method or the Fox method. When the sol-gel method or the silk method is employed, a coating liquid is coated on the cooled semiconductor wafer, then heated and cooled, and is cured, under heating and then cooling, in a low oxygen concentration atmosphere, thereby obtaining the interlayer dielectric film.
Here, the coating liquid is dropped at the center portion of a stationary semiconductor wafer and then the semiconductor wafer is rotated in order to extend the dropped coating liquid over the entire surface of the semiconductor wafer. Otherwise, the coating liquid is dropped onto a rotating semiconductor wafer.
In a spin-coating method as above-stated, most of the dropped coating liquid is spilt from the semiconductor wafer, and the spilt liquid is recovered and reused, or abandoned. However, it is costly to recover and reuse the wasted coating liquid, while it is also costly, if new coating liquid is purchased, always when it is needed, without recovery and reuse. Therefore, it is desired to minimize the amount of the coating liquid every coating process in order to reduce the cost of manufacturing the coated film on the semiconductor wafer.
Further, there is a problem that the coating film formation on the wafer by the spin-coating method tends to bring about the difference in film thickness between the center and the circumference of the wafer.